Today's television receivers are increasingly likely to provide special graphics features such as closed captioning and on-screen displays. The information for closed captioning is a part of the standard television broadcast signal, for example, line 21 of the NTSC signal. The information for on-screen displays is provided by a hand-held remote control unit, with which the user changes operating parameters such as channel and volume. The remote control unit transmits infra-red signals, which the television receiver detects to display channel and other control-related information on the display screen.
In existing receivers, devices for detecting closed captioning and on-screen display information provide analog outputs. These devices are suitable for analog displays, such as cathode ray tubes. However, their analog output is not useful for digital displays, such as spatial light modulators, which have an array of pixel elements that are addressed with digital display data. For SLMs, the analog closed captioning and on-screen display signals must be converted to digital form.
Another characteristic of SLMs is the use of "staggered" pixel arrays, in which the pixel elements are not laid out in square grid patterns. These staggered patterns are advantageous in terms of overall picture quality. However, when the image contains a vertical line, the line may appear jagged, an effect that is especially apparent in the characters used for closed captioning and on-screen displays.